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Patient presents with severe visual dysfunction and striking unilateral retinal appearance

A young woman had experienced decreasing vision in her right eye since she was 12 years old.

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Vitreoretinal surgeons must not only have steady hands and demonstrate appropriate surgical technique in the operating room, but they must also be skillful diagnosticians. This often involves gathering a careful history before performing a thorough eye examination. Ultimately, the clinician must create a reasonable differential diagnosis based upon all the information gathered. Herein, we present the case of a young woman who presented with a limited history but a striking eye examination, which may challenge ophthalmologists to form a differential diagnosis.

The case

A 31-year-old woman presented to the retina clinic after having been sent by another ophthalmologist for a second opinion regarding chorioretinal scarring in the right eye. The patient stated she had long-standing poor vision in the right eye ever since she was 12 years old and lived in Hawaii. She felt that her vision had decreased rather abruptly at that time and that, during recent years, her vision had slowly gotten worse in the right eye. The patient’s medical history was significant for the factor V Leiden mutation with a prior blood clot, but she was otherwise healthy. She worked as a clinical pharmacist at a hospital. She denied flashes, floaters, light sensitivity, recent illness and any history of trauma to the eye. The patient took a multivitamin regularly but was not on any other medication.

A complete review of systems and family history was negative with the exception of the factor V Leiden mutation in several family members. Ocular history was significant for a severe loss of vision in the right eye when the patient was 12 years old, during which time the physicians who treated her were unsure of the diagnosis but claimed that it involved “inflammation.” She had been treated with steroids. The patient stated that while growing up she was able to see the “big E” on the eye chart but was currently unable to do so.

Best corrected visual acuity was hand motion vision in the right eye and 20/15 in the left eye. The patient had a 3+ relative afferent pupillary defect in the right eye. IOP was 15 mm Hg in the right eye and 16 mm Hg in the left eye. Extraocular movements were normal in both eyes. Confrontational visual fields were unable to be performed in the right eye and were normal in the left eye. Anterior segment examination revealed a 2+ posterior subcapsular cataract in the right eye and a clear lens in the left eye. Otherwise, the anterior segment examination was normal.

Posterior segment examination of the right eye demonstrated a severely abnormal fundus with diffuse pigmentary changes in the macula and the retinal periphery (Figure 1). The retinal vasculature was attenuated, and the optic nerve demonstrated subtle temporal pallor. The retinal pigment epithelium appeared diffusely atrophic, and the fundus had a yellow appearance. There was an absence of vitritis. Posterior segment examination of the left eye was normal (Figure 2).

 

Figure 1. Wide-field color image of the right eye fundus demonstrating diffuse pigmentary changes in the macula and retinal periphery, retinal vascular attenuation, and a lenticular opacity obscuring the central macula.

 

Figure 2. Wide-field color image of the left eye fundus demonstrating a normal macula and retinal periphery with normal retinal vascular caliber.

Source: Kiss S, Witmer MT

Optical coherence tomography of the right eye demonstrated a severe loss of the outer retinal structures within the macula, including diffuse atrophy of the retinal pigment epithelium (Figure 3). The four outer retinal hyperreflective lines seen with a normal OCT (external limiting membrane, inner segment/outer segment junction, and dual layers of the retinal pigment epithelium) were severely disrupted; however, the outer retinal architecture of the foveal region of the right eye remained relatively preserved. OCT of the left eye was normal (Figure 4).

The diagnosis

The differential diagnosis of unilateral diffuse pigmentary changes in the retina includes diffuse unilateral subacute neuroretinitis (DUSN), unilateral retinitis pigmentosa, siderosis, trauma, acute zonal occult outer retinopathy, paraneoplastic syndromes such as cancer-associated retinopathy, rubella and syphilis, among others.

The patient reported that at the time of diagnosis of her eye problem, she was told she had an eye infection that was causing inflammation and was subsequently told her diagnosis was DUSN. No worm was ever identified on examination of her eye. Given her strikingly unilateral presentation, her lack of history of eye trauma, her lack of history of systemic infection or neoplasm, and negative family history of eye disease, DUSN appeared to be the most likely diagnosis.

DUSN is a rare retinal infection that occurs in healthy individuals due to a nematode. The roundworm is a parasite that travels subretinally and may cause significant retinal damage and vision loss if not identified and destroyed. Wilder was the first to identify nematodes as a source of retinal infection; however, Gass and others were the first to refer to the condition as DUSN.

Manifestations of the disease can be divided into acute and chronic. During the acute phase, patients often present with decreased vision. The eye may exhibit findings such as vitritis, optic neuritis, retinitis and crops of gray-white lesions in the outer retina. In up to 50% of cases, the subretinal nematode may be identified upon ophthalmologic examination, as it moves within the subretinal space. The chronic phase of the disease, on the other hand, often presents with diffuse retinal pigmentary changes, optic atrophy and retinal vascular attenuation.

A recent report of 121 patients with DUSN found that almost 70% of the patients were younger than 20 years old, and that while 7% of patients presented in the acute stage, 93% presented in the late stage. The subretinal nematode was identified in only 40% of patients.

The organisms responsible for the infection include Ancylostoma caninum and Baylisascaris procyonis, among others.

The management and treatment of the disorder consists of a prompt and thorough search for the nematode within the retina and focal photocoagulation until the worm is killed. In some patients, treatment with oral albendazole has been attempted and demonstrated success.

Our patient was instructed to follow monocular precautions, including the routine use of protective eyewear with polycarbonate lenses. She inquired about whether this could affect her fellow eye, and we informed her that, although possible, bilateral DUSN is exceedingly rare.